1. Field of the Invention
This invention relates in general to the construction of guns and, in particular, to a new and useful compressed air operated gun having a spring-loaded compression piston and a breech housing mounted within a housing or sleeve of the firearm which is displaceable relative to the mounting sleeve and which includes a power accumulator between the relatively moving parts for establishing equilibrium therebetween and for absorbing the frictional and operational forces.
2. Description of the Prior Art
During the firing of air guns, a relatively high motion impulse is produced due to the compression piston which is driven in the firing direction by a strong spring. This motion impulse causes the recoil if it is not compensated within the arm. The recoil is disagreeable to the shooter and also prevents an accurate hit, because during the relatively long development of the discharge, the air gun is slightly thrown off the line of sight. That is why recoilless air guns have been developed which compensate the motion impulse of the compression piston and rest relatively quitely in the hand of the shooter during the discharge.
In a known air gun of this kind the entire system, or at least the breech housing and the barrel, is mounted on the stock of the arm displaceably, to obtain a freedom from recoil. Thus, at the discharge, the stock remains immobile while the system accelerated by the motion impulse of the compression piston is moved against the motion direction of the latter. The system comes to rest only after the compression piston, at the end of its travel, abuts against the cylinder head whereby its kinetic energy is compensated with that of the system. At this moment, however, the projectile has already left the barrel so that it can no longer be effected by the impact shock. The system is mounted on the stock by means of several friction bearings or leaf springs positioned transversely to the motion direction or by means of rolling bodies mounted in bearings.
Another known air gun operates on the same principle as described above. There is a difference, however, in that the breech housing and the barrel rigidly connected thereto are mounted for longitudinal displacement in a guide jacket tube which is secured to the stock.
Although these known compressed-air firearms are called recoilless, they are not completely free from shocks and deviations of the stock and the system during the firing, and particularly during the time of the discharge development. In contradistinction to the shocks produced at the impact of the compression piston on the cylinder head, these irregularities affect the motion direction of the projectile still moving through the barrel which is, of course, undesirable. These disturbances are not excessive but they are perceived by the shooter and may be quantitatively determined by measuring instruments. Such measurements have shown that at the firing, the guns are deviated mainly in the vertical plane by a rotational motion about their transverse axis and that the barrel muzzle is swung upwardly. A small recoil of the stock has also been determined. As compared to that, the measured transverse oscillations are relatively unimportant.
In searching for the disturbance variables causing these undesirable deviations, it has been found that the main cause is the unavoidable friction forces between the system and the stock. Basically, this finding is not new and an effort has already been made in the known air gun to minimize the friction forces by attempting to mount the system on rollers, for example. In such a mounting on rollers, the system is equipped at each end with two bearing bolts disposed at an angle to each other on which the runners are rotatably mounted. The runners roll on correspondingly obliquely positioned plane surfaces of two bearing members which are screwed to the stock. To prevent the system from being lifted from the bearing surfaces, there is provided a spring-loaded retainer which acts against the movable system by means of further axially mounted rollers pressing on the bearing surfaces.
However, as compared to the pure sleeve mounting, this kind of antifriction mounting has the disadvantage of being very expensive because many different component parts partly difficult to manufacture are needed, such as, bearing recesses, pieces with bores, journals, rollers, a retainer and prismatic parts of the bearing. Aside from these expensive parts, the remaining friction forces are in no way minimal because, due to the retainer, the forces acting on the system are considerably increased and the rolling bodies must be mounted on journals whereby the rolling friction is yet increased by the journal friction and the friction of the lateral guidance of the rollers. Additionally, the axially mounted rollers must have a relatively large diameter and consequently, their flywheel effect which increases with the square of the diameter, is no longer negligible. The flywheel effect is detrimental insofar as, the acceleration of the system, and therefore, of the rollers, it produces a reaction force upon the stock in the direction of the friction force. This is why the known roller mounting has been used in experimental constructions, but is not generally used in practice.
The mobile mounting of the system on the stock by means of leaf springs deflectable in the longitudinal direction of the gun is also unsatisfactory. The leaf springs must be relatively very stiff in order not to buckle under the weight of the system and to permit an exactly linear lateral guidance. As the system is displaced relative to the stock during the firing, the leaf springs are moved along and return forces are produced corresponding to the stiffness of the spring, which act directly on the stock and result in a minor recoil. Moreover, the return forces also produce tilting moments in the system and the stock which tends to turn these parts in the same direction which naturally affects the shooting accuracy. In addition, tilting moments are also produced in other seats or bearings by the friction forces because, for constructional reasons, the centers of gravity of the system and the stock cannot be positioned in the action plane of the friction forces.
Another drawback of the mobile mounting by means of leaf springs is the fact that after the discharge, the springs retransfer the deformation energy to the system and move the same back in the opposite direction. This "counter-recoil" into the initial position is certainly desirable but necessarily entails clattering after-oscillations of the gun.